The new calcium antagonist isradipine was compared with nifedipine retard in a multicenter, double-blind, placebo-controlled, randomized study involving 159 patients with mild hypertension. A 2-week run-in period was followed by a 6-week course of treatment with the possibility of dose doubling after 3 weeks, depending on blood pressure (BP) response (target diastolic BP less than 90 mm Hg). Systolic and diastolic BPs were reduced by isradipine (mean dose of 3.6 mg daily) from 151/101 to 136/89 mm Hg, by nifedipine (mean dose of 50 mg daily) from 155/101 to 144/90 mm Hg, and by placebo from 155/101 to 154/99 mm Hg. Normalization rates were 64% with isradipine, 56% with nifedipine, and 16% with placebo. Adverse events consisted mainly of flushing, headache, edema, and dizziness. Altogether, 8 patients receiving isradipine experienced adverse events in comparison to 21 taking nifedipine and 4 taking placebo. The superior tolerability of isradipine was paralleled by a significant improvement in the subjective well-being of the patients as assessed by the von Zerssen questionnaire (List of Complaints). With nifedipine and placebo, no statistically significant improvement was observed.